Modified oriented polyacetal product

ABSTRACT

There are disclosed a modified oriented polyacetal product, the surface of said product being coated partly or entirely with a phenolic compound-polyacetal composite layer, the application thereof and a process for preparing the same.

This application is a continuation, of application Ser. No. 07/820,381filed on Jan. 14, 1992, now abandoned, which is a Rule 60 divisionalapplication of Ser. No. 07/263,405 filed on Oct. 27, 1988, now U.S. Pat.No. 5,098,787.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to oriented polyacetal products which havemodified surfaces, particularly to such products having surfaces withimproved affinity for other materials. The present invention alsorelates to a process for producing such products.

2. Discussion of the Related Art

By virtue of their high tensile strength and being superior in fatigueendurance, chemical resistance, and water repellency, polyacetals areused extensively as engineering plastics or as raw materials ofsynthetic fibers in various areas. In recent years, improvements ofpolyacetals of high elastic moduli and high strength have beendeveloped, and as a result they have come to attention as materialssuitable for composites with elastomers, plastics, or other materials.

However, because of the deficiency of polyacetals in their affinity fordissimilar materials, there have been difficulties in adheringpolyacetals firmly to such materials, and when polyacetals are subjectedto treatments such as plating, painting, coating, or printing, it isdifficult to fix the applied material securely on their surfaces.

To overcome these difficulties, various surface treatments are have beenpracticed including; mechanical surface roughening with sandpaper orsandblasting; physical surface etching by corona discharge, plasmadischarge, or the like; and chemical surface etching with potassiumdichromate, phosphoric acid, fluorine, or other reagents. But, thesetreatments only have some adhesion-enhancing effect based on physicalactions such as an anchor action, which hardly achieve anyadhesion-enhancing effect based on chemical bonds. Therefore, the resultof these treatments are not always satisfactory in the permanency of,peel resistance, or dynamic-fatigue resistance of the bond. The abovetreatments have also little adhesion-enhancing effect, because noncrystalline portions that are relatively receptive to chemical etchingare decreased by molecular orientation and hence these oriented polymersare virtually chemically inert.

On the other hand, British Patent No. 941,647 discloses a methodcomprising coating a polyacetal or other plastics to which it is to beadhered, with an unoriented polyacetal solution in a fluorine-containingorganic solvent such as 2H-hexafluoro-2-propanol, and adhering the twomaterials together and evaporating the solvent from the applied solutionto form an unoriented polyacetal coating. Also disclosed is a methodcomprising coating a metal or other materials to which a polyacetal isto be adhered, with such a solution as mentioned above, followed byevaporation. That is, these methods comprise interposing an unorientedpolyacetal layer between a polyacetal and the intended adherentmaterial. Besides 2H-hexafluoro-2-propanol, a number of organic solventsincluding phenols such as p-chlorophenol have been investigated up tonow to dissolve polyacetals [J. Polym. Sci., Vol. 34, p. 185 (1959)].According to the present inventors' study, however, the adhesivestrength of roughened surfaces of unoriented polyacetals to rubbers,when the surfaces were coated with an unoriented polyacetal solution inthe above-mentioned fluorine-containing organic solvent, or in a phenol,and dried, was decreased relative to the case where no such solution wasapplied. The same treatment of oriented polyacetals was found todecrease the adhesive strength similarly to the effect noted for thetreatment of the unoriented polyacetals, and thus no useful effect fromthe treatment was observed. The use of adhesives of the epoxy resin typefor the bonding also exhibited no adhesion-enhancing effect.

Moreover, none of the resorcinol-formaldehyde-rubber latex agedproducts, viz. RFL., and the initial stage condensate of resorcinol withformaldehyde viz. resol, which are well known as adhesives forrubber-reinforcing fiber cords and as adhesives for wood, exhibit anyeffect of enhancing the adhesive strength of polyacetals.

The reason why polyacetals are lacking, as described above, in affinityfor dissimilar materials is that polyacetals, unlike nylons andcellulosics that are highly polar, have no functional group at thesurface. Molecular orientation makes this tendency more noticeable.

SUMMARY OF THE INVENTION

The present inventors made intensive studies for the purpose ofdeveloping oriented polyacetal products which have high affinity fordissimilar materials. As a result, it has been found that when surfacesof oriented polyacetal products are treated with a phenolic compoundunder specific conditions, polyacetal-phenolic compound composite layershaving high affinity for dissimilar materials are unexpectedly formed onthe surfaces. Based on this finding, the present invention has beenaccomplished.

That is, according to the present invention, there are provided (i) amodified oriented polyacetal product, the surface of said product beingcoated partly or entirely with a polyacetal-phenolic compound compositelayer, (ii) various articles based on said product by modifying it inaccordance with the intended end uses of the individual articles, and(iii) processes for producing said product and articles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block flow diagram showing an example of a productionprocess for carrying out the present invention. In this drawing,reference letters and number indicate the following: A: an orientedpolyacetal product, 1: a feed roller, 2: a surface-roughening section,3: an activating section, 4: a heat treatment section, 5: an adhesiveapplying section, 6: a heat treatment section, and 7: a winding roller.

FIGS. 2 and 3 are perspective views of specimens assembled for measuringthe adhesive strength of a surface-modified oriented polyacetal productto partner materials with which composites are formed. In thesedrawings, reference letters are as follows: B: the specimen of thesurface-modified oriented polyacetal, C: the specimen of one of the twomaterials which consists mainly of an elastomer, and D: the specimen ofthe other of the materials which consists mainly of a plastic.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Any acetal homopolymers and copolymers may be used as a base materialfor the surface-modified oriented polyacetal product (forsimplification, "product" is often omitted herein after) of the presentinvention. The homopolymers are produced usually by polymerizingformaldehyde in the presence of an ionic polymerization initiator andhave number average molecular weights of 15,000 to 200,000 (MI 0.1-50),preferably 25,000 to 100,000 (MI 0.5-30). The copolymers are typicallypolyoxymethylene copolymers having one or more types of ether segmentsor polyether segments in the molecular chain. Such copolymers aregenerally produced by copolymerizing a cyclic ether with at least onealkylene oxide and have number average molecular weights of 10,000 to200,000 (MI 0.1-50), preferably 20,000 to 100,000 (MI 0.5-30). Examplesof such copolymers include those having 90-99.6 mole %, preferably95-99.6 mole %, of recurring oxymethylene units and 0.4-10 mole %,preferably 0.4-5 mole %, of ether segments which have each at least twocarbon atoms and are scattered in the molecular chain. When the contentof oxymethylene units is less than 90 mole %, the strength and elasticmodulus of the copolymer are undesirably low and when this contentexceeds 99.6 mole %, the strength and elastic modulus of the copolymerare substantially equal to those of the homopolymer.

In the present invention, the above defined polyacetal is used in auniaxially or polyaxially oriented state. Such oriented polymers areusually produced from unoriented polyacetals prepared by melt extrusionor the like, by molecular orientation according to, for example, thestretching, rolling, or hydrostatic-extruding method. These orientedpolyacetals can be used generally when having tensile elastic moduli atleast 4 GPa and tensile strengths of at least 0.6 GPa. It isadvantageous to use oriented polyacetals of higher elastic moduli andhigher strengths, that is, those having tensile elastic moduli of 10 GPaand more, preferably 20 GPa and more, particularly 30 GPa and more, andtensile strengths of 1.0 GPa and more, preferably 1.3 GPa and more,particularly 1.5 GPa and more.

The shape of these oriented polyacetals for use in the present inventionis optional. Any shape can be used that is chosen as desired fromshapes, for example, of films, sheets, filaments, blocks, tubes, rods,spheres, pellets, and flakes.

In the next place, the phenolic compound to be used in the presentinvention to form a composite layer jointly with a surface part of theabove defined oriented polyacetal is an aromatic compound having atleast one aromatic ring and at least one hydroxy group linked to thearomatic ring. Besides the hydroxy group, this phenolic compound mayhave one or more substituents including alkyl, haloalkyl, hydroxyalkyl,aminoalkyl, alkenyl, alkynyl, aryl, halogen, formyl, carboxy, carbonyl,ether, epoxy, amino, imino, cyano, cyanoacryloyloxy, acryloyloxy, nitro,sulfo, mercapto, triazinyl, acyl, carbamoyl, and thiocarbamoyl radicals.Such phenolic compounds include, for example, phenol, resorcinol,catechol, hydroquinone, pyrogallol, phloroglucin, aminophenol,dihydroxyaniline, cyanophenol, nitrophenol, picric acid, cresol,xylenol, carvacrol, thymol, naphthol, resorcinolaldehyde,resorcinolhydroquinone, salicylic acid, hydroxybenzoic acid,hydroxyphenylacetic acid, protocatechuic acid, gentisic acid, resorcinolacid, orsellinic acid, caffeic acid, umbellic acid, gallic acid,3-hydroxyphthalic acid, bisphenol A,2,2-bis (4-hydroxyphenyl)hexafluoropropane; halophenols such as chlorophenol, bromophenol, andpolyhalophenols; hydroxybenzyl alcohols such as monohydroxybenzylalcohol, dihydroxybenzyl alcohol, and trihydroxybenzyl alcohol;m-hydroxybenzylamine, and p-hydroxybenzylsulfonic acid. Of thesecompounds, preferred are dihydroxybenzenes such as resorcinol, catechol,and hydroquinone; trihydroxybenzenes such as pyrogallol; aminophenolssuch as aminophenol and dihydroxyaniline; halophenols such aschlorophenol; and hydroxybenzyl alcohols. These phenolic compounds maybe used alone or in combination one with another. Moreover, a mixture ofeach phenolic compound with either a resorcinol-formaldehyde condensateor a resorcinol-formaldehyde-latex aged product can be used effectivelyas a liquid for the treatment. The use of this mixture to adhere theoriented polyacetal to other materials, particularly to rubbers,provides adhesion much stronger and more resistant to thermal ageingthan does the use of the phenolic compound alone. Theresorcinol-formaldehyde condensate, usually called RF, is produced bythe reaction of resorcinol with formaldehyde either in the absence ofany catalyst or in the presence of an acid or alkali catalyst. In thisreaction, up to 2 moles of formaldehyde is used per 1 mole ofresorcinol. The aged resorcinol-formaldehyde-latex, usually called RFL,is produced by adding a latex to said RF and aging the mixture. Suitablelatexes for this RFL include a natural rubber latex, styrene-butadienerubber latex, vinylpyridine terpolymer latex, nitrile rubber latex,silicone rubber latex, urethane rubber latex, chlorosulfonated-polymerlatex, polyvinyl chloride latex, polyvinylidene chloride latex, andmixtures of these latexes. For adhering the oriented polyacetal tovulcanized rubbers, preferred latexes are of natural rubber,styrene-butadiene rubber, vinylpyridine terpolymer, and nitrile rubber.

When a solution of the phenolic compound is used for the treatment, theconcentration of phenolic compound is generally at least 10% by weight,preferably at least 20% by weight, particularly preferably from 30% byweight, to saturation. When the RF-phenolic compound mixture is used foradhering rubbers, the content of RF as solids in the mixture isgenerally from 0.01 to 2 parts by weight per 1 part by weight of thephenolic compound. If this content is less than 0.01 part by weight, theeffect of the RF will not be exhibited sufficiently. If the contentexceeds 2 parts by weight, an adverse effect will be producedoccasionally. As to the ratio of RFL to the phenolic compound, thecontent of RFL as solids is generally from 0.02 to 0.2 part by weightper 1 part by weight of the phenolic compound. If this content is lessthan 0.02 part by weight, the effect of the RFL will not be exhibitedsufficiently. If this content exceeds 0.2 part by weight, again anadverse effect will be produced occasionally.

There is no particular restriction on the means of applying the abovestated modifying agents on the oriented polyacetal. Generally, thesurface to be treated of the oriented polyacetal is contacted oroverlaid with each modifying agent by dipping, painting, spraying,placing in an atmosphere of gasified modifying agent, or other methodsand the resulting polyacetal is subjected to heat treatment at atemperature of up to the melting point, preferably the softening point,of the polyacetal, whereby a surface-modified oriented polyacetal can beprepared. The heat treatment can be generally completed in a period of10 seconds to 10 minutes at temperatures of 100° to 190° C. dependingupon the shape of the oriented polyacetal to be modified and the speciesof phenolic compound used. When the oriented polyacetal is treated bycontacting with the phenolic compound in melted or gaseous form, thecontact is generally complete in 0.1 to 10 seconds. Prior to thesetreatments, the surface to be modified of the oriented polyacetals maybe roughened by conventional methods to enhance the wettability andincrease the specific area of the surface, thereby facilitating thetreatments. It is also possible to accelerate the treatment byconducting it in the presence of an acid, alkali, or peroxide as acatalyst. Moreover, copolymerization or crosslinking can be causedsimultaneously with the formation of the composite layer by the jointuse of ammonia, an amine, alcohol, epoxy compound, acrylic compound,isocyanate compound, peroxide, or crosslinking agent.

The chemical structure of the composite layer thus formed at a surfaceof the oriented polyacetal is not yet elucidated, but the compositelayer may have a structure wherein; a strong intermolecular force causesthe molecules of the phenolic compound to be an inclusion in a networkof polyacetal molecules; the polyacetal and the phenolic compound are ina chemically combined state; or both the states coexist. The compositelayer may not necessarily arise simply from the physical adsorption ofphenolic compound on the surface of polyacetal. This assumption issupported by the facts that after the formed composite layer is washedseveral times with a solvent of phenolic compounds, no weight loss isobserved; that absorptions typical of a phenolic resin component areobserved in the infrared absorption spectra of parts of the compositelayer; and that absorptions typical of a similar phenolic resincomponent are also observed in the infrared absorption spectra ofsamples prepared by dissolving parts of the composite layer in a solventfor the polyacetal and drying up the solution.

It is conceivable that the composite layer formed on the orientedpolyacetal surface modified by treating with a mixture of the phenoliccompound and either RF or RFL is in a state where RF or RFL are occludedin a network of phenolic resin which is formed by the reaction of thephenolic resin with a part of the polyacetal.

The modified oriented polyacetal of the present invention may be coveredentirely or partly with the composite layer. Depending upon conditionsof the treatment, the thickness of .the composite layer ranges generallyfrom several μm to several mm.

Further, adhesives suitable for the end uses of the above individualmodified oriented polyacetal products can be applied on surfaces of theproducts. These adhesive-coated, modified, oriented polyacetal productsmay be coated with dissimilar materials or used to form composites withthem. For instance, when the modified oriented polyacetal is coated withan elastomer or used as a reinforcement for an elastomer, an adhesivefor elastomer purposes is applied on the modified oriented polyacetal. Aproper adhesive is chosen according to the kind of elastomer used. Thereis no particular restriction on the elastomer to use. An arbitrary onecan be chosen from conventional elastomers. Suitable elastomers include,for example, natural rubber, SBR, IR, BR, EPR, butyl rubber,polyisobutylene, chloroprene rubber, neoprene rubber, NBR, polyurethanerubber, polysulfide rubber, halogenated rubber, acrylic rubber,chlorohydrin rubber, fluororubber, silicone rubber, variousthermoplastic elastomers, and compositions of these elastomers, thoughnot limited to these elastomers.

As to favorable adhesives for these elastomers, RFL's are used generallyfor vulcanized rubbers, polyvinyl chloride latexes are used forpolyvinyl chloride, polyvinylidene chloride latexes are used forpolyvinylidene chloride, and urethane rubber latexes are used forpolyurethane. Other suitable adhesives for the elastomers include thoseof the urea family, melamine family, isocyanate family, phenolic family,polyamide family, urethane family, cyanoacrylate family, acrylic family,polyester family, nitrocellulose family, vinylacetate resin family,epoxy resin family, vinyl acetal family, and vinyl alcohol family, anddenatured products from these adhesives.

When the modified oriented polyacetal is coated with a plastic or usedas a reinforcement for a plastic, an adhesive suited to the plastic ischosen and used. There is no particular restriction on the plastic. Forexample, usable plastics are epoxy resins, polyamide resins, polyesterresins, polyolefin resins, polyether resins, polycarbonate resins, urearesins, silicone resins, fluoro resins, vinyl chloride resins,vinylidene chloride resins, acrylic resins, phenolic resins, polyvinylalcohol resin, polysulfone resins, polystyrene-resins, polyethersulfoneresins, polyphenylene sulfide resins, and compositions of these resins,though not limited to these. For adhering plastics, adhesives suited foreach plastic are used.

As the occasion demands, the surface-modified oriented polyacetal of thepresent invention can be formed into composites with concrete, papers,woods, metals, metal compounds, glasses, ceramics, leather, etc.,besides elastomers and plastics, by applying adhesives suited for thepurposes of individual products.

For the purpose of providing chemical and/or physical properties topolyacetals which will be used in the present invention, it is possibleto incorporate into them various elastomers, e.g., polyamide elastomers,polyester elastomers, and polyurethane elastomers, glass fiber, carbonblack, polyurea, polythiourea, phenol resins, urea resins, etc.Moreover, intended properties can be imparted to the polyacetal, ifnecessary, be incorporating additives such as antioxidants, heatstabilizers, flame retardants, oils, lubricants, plasticizers,antistatic agents, colorants, and softening agents and various fillers,e.g. carbon fiber whiskers, synthetic fibers, and ceramics.

Referring now to the accompanying drawings, the process of the presentinvention will be described illustratively. FIG. 1 is a block diagramshowing an example of a continuous process for producing asurface-modified oriented polyacetal in accordance with the presentinvention. As shown in FIG. 1, an oriented polyacetal A is sent from afeed roller 1 to a roughening section 2, where a surface of thepolyacetal A is roughened, then in an activating section 3 the toughenedsurface is coated with a phenolic compound or its mixture with RF orwith RFL as stated above, the coated polyacetal is heated in a heattreating section 4, then the coated surface is overlaid with an adhesivelayer by passing the polyacetal through an adhesive applying section 5and then a heat treating section 6, and the resulting treated polyacetalis wound up around a winding roller 7. When a phenolic compound in amolten or gaseous state is used in this process, the polyacetal in theactivating section 3 is activated by contact with the phenolic compoundand simultaneous reaction therewith. In the process of FIG. 1, othertreatment sections can be incorporated, if necessary, such as a take-upand take-off section, annealing section, and cooling section. The heattreatments in sections 4 and 6 can be carried out by conventionalheating means including external heating means, e.g. steam andelectrical heaters, and internal heating means using, e.g.high-frequency waves, infrared rays, far infrared rays, and lasers.

The modified oriented polyacetal of the present invention, havingphenolic hydroxy groups and other functional groups at the modifiedsurface, is superior in reactivity and chemical affinity of the modifiedsurface, which therefore exhibits firm and permanent adherence onsticking, plating, painting, coating, dyeing, printing, etc. Inaddition, the modified oriented polyacetal product prepared by applyingan adhesive on the modified surface according to the end use of theproduct, when adhered to dissimilar materials, forms firm and permanentbonds which are superior in dynamic-fatigue endurance, peel resistance,thermal-degradation resistance, etc. The adhesive strength of thesecomposites to dissimilar materials is at least 150 g/mm² in general, atleast 250 g/mm² in favourable cases, at least 300 g/mm² in morefavourable cases, at least 380 g/mm² in particularly favourable cases,and 1500 g/mm² at the highest.

Oriented polyacetals for use in the present invention have not only highelastic moduli and high tenacity but also a specific gravity up to 5.5times lower than that of steel, do not buckle, and are good in manyrespects including flextural fatigue endurance, durability, creepresistance, moderateness of elongation, hardness, S--S properties,dimensional stability, low thermal shrinkage, coefficient of linearexpansion, heat resistance, chemical resistance, sea water resistance,solvent resistance, hot water resistance, corrosion resistance,cryogenic temperature resistance, safety, and shapability. Orientedpolyacetals in fibrous form of 0.01 μm to several mm diameter areavailable. In particular, those having diameters of mm orders have suchhigh tenacity that the strength of one filament thereof corresponds tothat of thousands to tens of thousands of conventional high tenacitysynthetic filaments. Accordingly, these oriented polyacetals can beprocessed very easily to form composites and have strengths, dimensions,shapes, and properties very close to those of conventional steel cords,and are available in any shape selected as desired from round rod,square rod, special profile, filament, staple, chip, tube, sheet, tape,film, and other shapes. The modified oriented polyacetal having suchcharacteristics of oriented polyacetals is may be used in a wide varietyof applications. These possible applications include articles necessaryto have high elastic moduli and high strength, for example, compositeswith elastomers such as tire cords, beads for tires, cable beads fortires, and paddings (reinforcements) of belts, hoses, pipes, sheets,diaphragm valves, snow chains, rolls, and of bearings; composites withplastics such as honeycombs, gear wheels, skis, fishing rods, printedcircuit boards, and sheets, plates, containers, and structures ofvarious fiber-reinforced plastics; civil engineering building materialsor various injection molded products reinforced with fibers such asreinforcements for concrete, fiber reinforcements for concrete slate,materials for concrete shield construction, and geogrid; elastomer-orresin-coated ropes, cables, tension members, braids, nets, tents, sails,filter cloths, canvases and apparel, sling belts, and other knitted,woven or unwoven fabrics; sporting or hobby goods, or home applicancessuch as guts, fishing lines, handicraft materials, art flowers,artificial lawn and brushes; materials for information or communicationmedia, such as base materials of recording tapes; and other compositeswith papers, pulps, woods, metals, metal compounds, glasses, ceramics,or leathers. Further, the thermoplastic nature of polyacetals modifiedaccording to the present invention enables them to be used in hot-meltadhesives and other various adhesives.

The present invention is illustrated in more detail with reference tothe following examples which are not intended to place any restrictionon the invention. In the following examples, oriented polyacetals wereprepared according to the method described in Japanese PatentApplication Kokai No. 60-183122. Properties of oriented polyacetals andtheir modification products were evaluated in the following ways.

(1) Tensile elastic modulus and tensile strength:

Determined in accordance with JIS K7113 (1981) by using an Instrontensile tester. The tensile elastic modulus was evaluated by using adifferential transformer type of strain gauge. The tensile strength wasevaluated by winding a test specimen several turns on two stainlesssteel reels with a diameter of 160 mm separated by 20 cm and drawing thespecimen at a strain rate of 10 cm/min. The cross-sectional area of thespecimen, necessary to calculate the tensile elastic modulus and thetensile strength, was calculated from the weight of the specimen havinga definite length and from the apparent density of the specimendetermined in the following way.

(2) Apparent density

Measured at 20°±0.5° C. in accordance with the sink and float method ofJIS K7112 (1980) by using an aqueous solution of anhydrous potassiumcarbonate as a medium of known density.

(3) Adhesive strength

Determined in accordance with JIS L 1017 (1983) method A (T test). Thatis, an end portion (10 mm long) of a surface-modified orientedpolyacetal specimen (B) 210 mm long was inserted into a compoundingpartner material, thereby preparing a composite specimen as shown inFIG. 2 or 3, and the stress (withdrawal force) exerted when thepolyacetal specimen was withdrawn from the partner material wasmeasured, thereby determining the adhesive strength from the followingequation. ##EQU1##

The diameter of the polyacetal specimen was calculated from its weightand apparent density.

FIG. 2 shows a polyacetal composite specimen wherein the compositepartner consists mainly of an elastomer and the cube C has the size: 10mmL×20 mmW×10 mmH. FIG. 3 shows a composite specimen wherein thecylinder D has dimensions of 10 mm Dia.×10 mmH.

(4) Preparation of samples

Preparation Example 1 Preparation of Phenolic Compound Solution

The phenolic compound to be used was dissolved in water or an organicsolvent at 23° C. to a concentration of 10% by weight to saturation,thereby making up the intended solution.

Preparation Example 2 Preparation of RF Liquid

A mixture of 16.2 parts by weight (hereinafter parts are all by weight)of resorcinol, 20.0 parts of formalin of 37 wt % concentration, 0.41part of sodium hydroxide, and 373.8 parts of water was stirred at 23° C.for 6 hours, thereby making up the intended RF liquid.

Preparation Example 3 Preparation of RFL Liquid

A mixture of 16.2 parts of resorcinol, 20.0 parts of formalin of 37 wt %concentration, 0.41 part of sodium hydroxide, and 373.8 parts of waterwas stirred at 23° C. for 6 hours. To the resulting liquid were added282.2 parts of a vinylpyridine terpolymer latex (solid content 40 wt %)(supplied by Sumitomo-Naugatuck Inc., tradename: Pyratex), 43.3 parts ofan SBR latex (solid content 32 wt %) (supplied by Nippon Zeon Co., Ltd.,tradename: J-9049), 11.8 parts of a natural rubber latex (solid content60 wt %)(supplied by HMPB Co., tradename: H & C), and 233.3 parts ofwater. This mixture was stirred at 23° C. for 24 hours and then 18.0parts of aqueous ammonia of 28 wt % concentration was added, therebymaking up the intended RFL liquid.

Preparation Example 4 Preparation of oriented polyacetal products

Pellets of Tenac 3010 (the registered trademark of an acetal homopolymersupplied by Asahi Chemical Co., Ltd.) were melt-extruded at 200° C. toprepare polyacetal tubes, which were then each stretched continuouslyunder pressure giving oriented polyacetal products having tensileelastic moduli of 4 to 55 GPa.

(5) Example of analyzing modified surfaces of oriented polyacetalproducts

An oriented polyacetal tape having a tensile elastic modulus of 40 GPawas treated with resorcinol, (a representative example of the phenoliccompounds usable in the present invention which exhibited the highestmodifying effect). Pieces of the oriented polyacetal cut into approx. 1cm lengths were immersed in a methanolic solution containing 40 wt % ofresorcinol, then removed, and air-dried, thereby coating resorcinoluniformly on the pieces. These pieces were subjected to dry heattreatment at 160° C. for 3 minutes, then washed three times withmethanol, and dried (the dried product is designated as sample 1). Thissample 1 showed about 4% increase in the weight over the untreatedpieces. On extraction with methanol for 1 hour, this sample showedlittle change in weight (the extraction product is designated as sample2). In the FT-IR spectra of surface portions of this sample 2,absorptions due to a form of resorcinol resin were observed. Then,surface layers of sample 2 were dissolved in hexafluoroisopropanol,methanol was added to the resulting solution, and the formed precipitatewas filtered and washed with methanol. After freeze drying of thefiltrate, resorcinol was found in the residual prepipitate. The aboveprecipitate filtered off was dried and kneaded together with KBr. Thekneaded mixture was dried, compressed, and subjected to FT-IRspetrometry. The spectrum showed absorptions due to polyacetal andabsorptions, though slight, due to a form of resorcinol resin. The aboveresults have revealed that resorcinol is strongly incorporated byreaction into the polyacetal.

EXAMPLES 1-7 AND COMPARATIVE EXAMPLE 1

Oriented polyacetals in filament form having properties shown in Table 1were each sandblasted with alumina of no. 120 grade, immersed in anaqueous solution containing 40 wt % of resorcinol for 30 seconds at 23°C., then taken out, subjected to dry heat treatment at 160° C. for 10seconds, immersed again in an aqueous solution of RFL (PreparationExample 3) at 23° C. for 30 seconds, then taken out, dried at 120° C.for 5 minutes, and heat-treated at 160° C. for 5 minutes. Each of thesetreated polyacetals and a compounded crude rubber for automotive tirecarcass purposes were put together, and heat-treated in a hot press at35 kg/cm² and 150° C. for 30 minutes to prepare a composite specimen asshown in FIG. 2. The oriented polyacetal was withdrawn from the rubberpiece to evaluate the adhesive strength. Results of the tests on all theabove treated oriented polyacetals are shown in Table 1. For comparison,the above procedure was followed except that the treatment withresorcinol was omitted. Results of this comparative experiment are alsoshown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________           Oriented polyacetal                                                           Tensile elastic                                                                       Tensile strength                                                                      Elongation                                                                          Diameter                                                                           Withdrawal force                                                                       Adhesive strength                         modulus (GPa)                                                                         (GPa)   (%)   (mm) (Kgf)    (g/mm.sup.2)                       __________________________________________________________________________    Example 1                                                                             4      0.6     20˜25                                                                         1.01 12.6     400                                Example 2                                                                            10      1.0     14˜16                                                                         0.80 15.1     600                                Example 3                                                                            20      1.3      9˜11                                                                         0.65 14.3     700                                Example 4                                                                            30      1.5     7˜9                                                                           0.58 18.2     1000                               Example 5                                                                            40      1.7     6˜8                                                                           0.50 18.0     1150                               Example 6                                                                            50      1.3     4˜6                                                                           0.44 15.9     1150                               Example 7                                                                            55      1.0     4˜6                                                                           0.44 8.2      600                                Comparative                                                                          40      1.7     6˜8                                                                           0.50 2.0      130                                Example 1                                                                     __________________________________________________________________________

As is evident from Table 1, the surface-modified oriented polyacetal ofthe present invention has markedly strong adhesion to the rubber.

EXAMPLES 8-20 AND COMPARATIVE EXAMPLE 2

The same oriented polyacetals in filament form as used in Example 5 wassandblasted with alumina of No. 120 grade, each immersed in solutions of40 wt % of various phenolic compounds listed in Table 2 for 30 seconds,then taken out, and subjected to dry heat treatment at 160° C. for 10seconds. Thereafter, RFL treatment and then rubber adhesion wereconducted in the same manner as in Examples 1-7 to prepare compositespecimens. Results of testing these specimens for adhesive strength areshown in Table 2. For comparison, the above procedure was followedexcept that the treatment with phenolic compounds was omitted. Resultsof this comparative experiment are also shown in Table 2.

                                      TABLE 2                                     __________________________________________________________________________                Oriented polyacetal                                                                   Elastic modulus          Withdrawal                                                                             Adhesive strength                   Diameter (mm)                                                                         (GPa)   Phenolic compound (solvent)                                                                    (kgf)    (g/mm.sup.2)            __________________________________________________________________________    Example 8   0.5     40      Resorcinol (water)                                                                             18.0     1150                    Example 9   0.5     40      Phloramine (THF) 10.0     640                     Example 10  0.5     40      Catechol (water) 9.0      570                     Example 11  0.5     40      p-Chlorophenol (THF)                                                                           8.4      540                     Example 12  0.5     40      m-Aminophenol (THF)                                                                            8.0      510                     Example 13  0.5     40      m-Cresol (THF)   7.6      480                     Example 14  0.5     40      2,4-Dihydroxybenzaldehyde (THF)                                                                6.9      440                     Example 15  0.5     40      Gallic acid (THF)                                                                              6.5      410                     Example 16  0.5     40      Pyrogallol (THF) 6.1      390                     Example 17  0.5     40      3,5-Xylenol (THF)                                                                              5.9      380                     Example 18  0.5     40      o-Nitrophenol (THF)                                                                            5.4      340                     Example 19  0.5     40      Phenol (THF)     5.3      340                     Example 20  0.5     40      3,5-Dihydroxybenzoic acid (THF)                                                                4.9      310                     Comparative Example 2                                                                     0.5     40      None             2.0      130                     __________________________________________________________________________

It is considered that such strong adhesion to the rubber as shown inTable 2 results from the surface modification of the oriented polyacetalaccording to the process of the present invention. It may be noted thatoriented polyacetals washed with THF after treatment with phenoliccompounds exhibited similar adhesive strengths as well.

EXAMPLES 21-27 AND COMPARATIVE EXAMPLE 3

Oriented polyacetals in filament form having properties shown in Table 3were each sandblasted with alumina of No. 120 grade, immersed in amixture of 40 parts of resorcinol and 60 parts of an RF liquid (statedabove) for 30 seconds, then taken out, subjected to dry heat treatamentat 160° C. for 20 seconds, immersed again in an RFL liquid at 23° C. for30 seconds, then taken out, dried at 120° C. for 5 minutes, andsubjected to dry heat treatment at 160° C. for 5 minutes. Thereafter,rubber adhesion was conducted in the same manner as in Examples 1-7 toprepare composite specimens as shown in FIG. 2. Results of testing thesespecimens for adhesive strength are shown in Table 3. For comparison,the above procedure was followed but using an RF liquid (PreparationExample 2) as a modifying agent in place of the resorcinol-RF liquidmixture. Results of this comparative experiment are also shown in Table3.

As is evident from Table 3, the adhesive strength was enhanced by thetreatment with the resorcinol-RF liquid mixture. In Examples 23-26, muchrubber clung to the surface-modified oriented polyacetals afterwithdrawing thereof. The result of a thermal-ageing resistance test at121° C. for 24 hours showed that the polyacetal-rubber compositespecimen of Example 26 retained 80% of the original withdrawal-resistingforce.

                                      TABLE 3                                     __________________________________________________________________________           Oriented polyacetal                                                           Tensile elastic                                                                       Tensile strength                                                                      Elongation                                                                           Diameter                                                                           Composition of                                                                            Withdrawal                                                                          Adhesive strength               modulus (GPa)                                                                         (GPa)   (%)    (mm) modifying agent                                                                           force (kgf)                                                                         (g/mm.sup.2)             __________________________________________________________________________    Example 21                                                                            4      0.6     20˜25                                                                          1.01 Resorcinol + RF liquid                                                                    15.7  500                                                         (40 parts)   (60 parts)                    Example 22                                                                           10      1.0     14˜16                                                                          0.80 Resorcinol + RF liquid                                                                    17.6  700                                                         (40 parts)   (60 parts)                    Example 23                                                                           20      1.3      9˜11                                                                          0.65 Resorcinol + RF liquid                                                                    18.4  900                                                         (40 parts)   (60 parts)                    Example 24                                                                           30      1.5     7˜9                                                                            0.58 Resorcinol + RF liquid                                                                    21.0  1150                                                        (40 parts)   (60 parts)                    Example 25                                                                           40      1.7     6˜8                                                                            0.50 Resorcinol + RF liquid                                                                    21.0  1340                                                        (40 parts)   (60 parts)                    Example 26                                                                           50      1.3     4˜6                                                                            0.44 Resorcinol + RF liquid                                                                    18.5  1340                                                        (40 parts)   (60 parts)                    Example 27                                                                           55      1.0     4˜6                                                                            0.44 Resorcinol + RF liquid                                                                     9.7  700                                                         (40 parts)   (60 parts)                    Comparative                                                                          40      1.7     6˜8                                                                            0.50 RF liquid alone                                                                            2.0  130                      Example 3                                                                     __________________________________________________________________________

EXAMPLES 28-34 AND COMPARATIVE EXAMPLE 4

Oriented polyacetals in filament form having properties shown in Table 4were each sandblasted with alumina of No. 120 grade, immersed in amixture of 40 parts of resorcinol, 20 parts of an RFL liquid(Preparation Example 3), and 40 parts of water for 30 seconds at 23° C.,then taken out, subjected to dry heat treatment at 160° C. for 20seconds, immersed again in the RFL liquid at 23° C. for 30 seconds, thentaken out, dried at 120° C. for 5 minutes, and subjected to dry heattreatment at 160° C. for 5 minutes. Thereafter, rubber adhesion wasconducted in the same manner as in Examples 1-7 to prepare compositespecimens. Results of testing these specimens for adhesive strength areshown in Table 4. For comparison, the above procedure was followed butusing the RFL liquid alone as a modifying agent. Results of thiscomparative experiment are also shown in Table 4.

                                      TABLE 4                                     __________________________________________________________________________           Oriented polyacetal                                                           Tensile                                                                       elastic                                                                            Tensile                                                                  modulus                                                                            strength                                                                            Elongation                                                                          Diameter                                                                           Composition of    Withdrawal                                                                          Adhesive strength               (GPa)                                                                              (GPa) (%)   (mm) modifying agent   force (kgf)                                                                         (g/mm.sup.2)             __________________________________________________________________________    Example 28                                                                            4   0.6   20˜25                                                                         1.01 Resorcinol + RFL liquid + water                                                                 20.4  650                                                   (40 parts) .sup.    .sup. (20 parts).sup.                                     (40 parts)                                       Example 29                                                                           10   1.0   14˜16                                                                         0.80 Resorcinol + RFL liquid + water                                                                 21.4  850                                                   (40 parts) .sup.    (20 parts).sup.     (40                                   parts)                                           Example 30                                                                           20   1.3    9˜11                                                                         0.65 Resorcinol + RFL liquid + water                                                                 23.5  1150                                                  (40 parts) .sup.    (20 parts).sup.     (40                                   parts)                                           Example 31                                                                           30   1.5   7˜9                                                                           0.58 Resorcinol + RFL liquid + water                                                                 23.5  1300                                                  (40 parts) .sup.    (20 parts).sup.     (40                                   parts)                                           Example 32                                                                           40   1.7   6˜8                                                                           0.50 Resorcinol + RFL liquid + water                                                                 23.5  1500                                                  (40 parts) .sup.    (20 parts).sup.     (40                                   parts)                                           Example 33                                                                           50   1.3   4˜6                                                                           0.44 Resorcinol + RFL liquid + water                                                                 20.7  1500                                                  (40 parts) .sup.    (20 parts).sup.     (40                                   parts)                                           Example 34                                                                           55   1.0   4˜6                                                                           0.44 Resorcinol + RFL liquid + water                                                                 12.4  900                                                   (40 parts) .sup.    (20 parts).sup.     (40                                   parts)                                           Comparative                                                                          40   1.7   6˜8                                                                           0.50 RFL liquid alone   2.0  130                      Example 4                                                                     __________________________________________________________________________

As is evident from Table 4, the adhesion to the rubber was enhancedoutstandingly by the treatment with the resorcinol-RFL liquid mixture.In Examples 30-33, much rubber clung to the surface-modified orientedpolyacetals after withdrawing thereof. The result of a thermal-ageingresistance test at 121° C. for 24 hours showed that thepolyacetal-rubber composite specimen of Example 32 retained 80% of theoriginal withdrawal-resisting force.

EXAMPLES 35-39

The same oriented polyacetal in filament form as used in Example 25 wassandblasted with alumina of No. 120 grade. Then, composite specimenswere prepared from this polyacetal according to the procedure of Example25 except that resorcinol-RF liquid mixtures having differentcompositions as shown in Table 5 were used as modifying agent. Resultsof evaluating the adhesive strengths are shown in Table 5.

                                      TABLE 5                                     __________________________________________________________________________           Oriented polyacetal                                                           Tensile elastic                                                                       Tensile strength                                                                      Elongation                                                                           Diameter                                                                           Composition of                                                                            Withdrawal                                                                          Adhesive strength               modulus (GPa)                                                                         (GPa)   (%)    (mm) modifying agent                                                                           force (kgf)                                                                         (g/mm.sup.2)             __________________________________________________________________________    Example 35                                                                           40      1.7     6-8    0.50 Resorcinol + RF liquid                                                                    18.5  1180                                                        (10 parts)   (90 parts)                    Example 36                                                                           40      1.7     6-8    0.50 Resorcinol + RF liquid                                                                    19.0  1210                                                        (20 parts)   (80 parts)                    Example 37                                                                           40      1.7     6-8    0.50 Resorcinol + RF liquid                                                                    20.0  1270                                                        (30 parts)   (70 parts)                    Example 38                                                                           40      1.7     6-8    0.50 Resorcinol + RF liquid                                                                    21.0  1340                                                        (40 parts)   (60 parts)                    Example 39                                                                           40      1.7     6-8    0.50 Resorcinol + RF liquid                                                                    21.0  1340                                                        (50 parts)   (50 parts)                    __________________________________________________________________________

EXAMPLES 40-43

The same oriented polyacetal in filament form as used in Example 32 wassandblasted with alumina of No. 120 grade. Composite specimens wereprepared from this polyacetal according to the procedure of Example 32except that resorcinol-RFL liquid mixtures having different compositionsas shown in Table 6 were used as modifying agents. Results of evaluatingthe adhesive strengths are shown in Table 6.

                                      TABLE 6                                     __________________________________________________________________________           Oriented polyacetal                                                           Tensile                                                                       elastic                                                                            Tensile                                                                  modulus                                                                            strength                                                                            Elongation                                                                          Diameter                                                                           Composition of    Withdrawal                                                                          Adhesive strength               (GPa)                                                                              (GPa) (%)   (mm) modifying agent   force (kgf)                                                                         (g/mm.sup.2)             __________________________________________________________________________    Example 40                                                                           40   1.7   6-8   0.50 Resorcinol + RFL liquid + water                                                                 20.0  1270                                                  (40 parts) .sup.     (5 parts).sup.     (55                                   parts)                                           Example 41                                                                           40   1.7   6-8   0.50 Resorcinol + RFL liquid + water                                                                 21.5  1370                                                  (40 parts) .sup.    (10 parts).sup.     (50                                   parts)                                           Example 42                                                                           40   1.7   6-8   0.50 Resorcinol + RFL liquid + water                                                                 23.5  1500                                                  (40 parts) .sup.    (20 parts).sup.     (40                                   parts)                                           Example 43                                                                           40   1.7   6-8   0.50 Resorcinol + RFL liquid + water                                                                 23.5  1500                                                  (40 parts) .sup.    (30 parts).sup.     (30                                   parts)                                           __________________________________________________________________________

EXAMPLES 44 and 45

The same oriented polyacetal in filament form as used in Example 5 wassandblasted with alumina of No. 120 grade, immersed in a modifyingmixture of one of two phenolic compounds (see Table 7) with an RF liquid(Preparation Example 2) for 30 seconds at 23° C., then taken out, andsubjected to dry heat treatment at 160° C. for 20 seconds. Thereafter,RFL treatment and then rubber sticking were conducted in the same manneras in Example 5, thereby preparing composite specimens. Results ofevaluating adhesive strengths are shown in Table 7.

                                      TABLE 7                                     __________________________________________________________________________           Oriented polyacetal                                                           Tensile                                                                       elastic                                                                            Tensile                                                                  modulus                                                                            strength                                                                            Elongation                                                                          Diameter                                                                           Composition of    Withdrawal                                                                          Adhesive strength               (GPa)                                                                              (GPa) (%)   (mm) modifying agent   force (kgf)                                                                         (g/mm.sup.2)             __________________________________________________________________________    Example 44                                                                           40   1.7   6-8   0.50 Catechol + RF liquid                                                                            10.5  670                                                   (40 parts)   (60 parts)                          Example 45                                                                           40   1.7   6-8   0.50 Pyrogallol + RF liquid                                                                           7.1  450                                                   (40 parts)   (60 parts)                          __________________________________________________________________________

EXAMPLES 46-48 AND COMPARATIVE EXAMPLES 5

Pellets of Duracon M 25-04 (the registered trademark of an acetalcopolymer supplied by Polyplastic Co., Ltd.) were melt-extruded at 190°C. to prepare tubes of 2.4 mm outer diameter and 0.8 mm inner diameter.These tubes were stretched continuously under pressure, yieldingoriented polyacetal products having different properties as shown inTable 8. These oriented polyacetals were each sandblasted with aluminaof No. 120 grade, immersed in a modifying mixture of 40 parts ofresorcinol and 60 parts of an RF liquid (Preparation Example 2) for 30seconds at 23° C., then taken out, and subjected to dry heat treatmentat 160° C. for 20 seconds. Thereafter, RFL treatment and then rubberadhesion were conducted in the same manner as in Examples 21-27, therebypreparing composite specimens. Results of evaluating the adhesivestrengths are shown in Table 8.

                                      TABLE 8                                     __________________________________________________________________________           Oriented polyacetal                                                           Tensile                                                                       elastic                                                                            Tensile                                                                  modulus                                                                            strength                                                                            Elongation                                                                          Diameter                                                                           Composition of    Withdrawal                                                                          Adhesive strength               (GPa)                                                                              (GPa) (%)   (mm) modifying agent   force (kgf)                                                                         (g/mm.sup.2)             __________________________________________________________________________    Example 46                                                                           10   1.0   14-16 0.80 Resorcinol + RF liquid                                                                          16.3   650                                                  (40 parts)   (60 parts)                          Example 47                                                                           20   1.1    9-11 0.60 Resorcinol + RF liquid                                                                          17.0   900                                                  (40 parts)   (60 parts)                          Example 48                                                                           28   1.2   7-9   0.52 Resorcinol + RF liquid                                                                          17.0  1050                                                  (40 parts)   (60 parts)                          Comparative                                                                          28   1.2   7-9   0.52 RF liquid alone   17.0   120                     Example 5                                                                     __________________________________________________________________________

EXAMPLE 49

Pellets of Tenac 3010 were extruded through 20 holes of 0.60 mmφ of aspinneret at 200° C. by using an extruder. The extrudates were passedthrough a water bath and wound up to prepare unstretched yarns eachconstituted of 20 monofilaments each having a diameter of 0.15 min.These yarns were stretched continuously under pressure, yieldingstretched yarns consisting of 35 μm diameter monofilaments. The yarnswere found to have a tensile elastic modulus of 40 GPa, tensile strengthof 1.7 GPa, and elongations of 6 to 8%. The stretched yarns were treatedcontinuously as shown in FIG. 1, but the surface roughening was omitted.Conditions in the other sections were as follows: In the activatingsection 3, modifying agent: a resorcinol (40 parts)-RF liquid (60 parts)mixture, residence time: 16 seconds; in the heat treatment section 4,temperature: 160° C., residence time: 20 seconds; in the adhesiveapplying section 5, adhesive for elastomers: RFL liquid, residence time:16 seconds; in the heat treatment section 6, temperature: 180° C.,residence time: 1 minute. The thus treated yarns were wound up, yieldingsurface-modified stretched polyacetal yarns. Their elastic modulus,tensile strength, and adhesive strength (when these yarns were adheredto a rubber) were found to be 34 GPa, 1.6 GPa, and 1340 g/mm²,respectively. For comparison, a tire cord of 2520 d (monofilament size 6d, formed by twisting two 1260 d strands, cord diameter 0.56 mm) made ofnylon-66 was treated with an RFL liquid stated above according to theordinary method, and was adhered to the same rubber as used above. Theresulting adhesive strength was 970 g/mm². As shown above, polyacetalcords surface-modified according to the present invention can be adheredmore strongly to elastomers than conventional tire cords can be.

EXAMPLE 50

An oriented polyacetal in filament form of 1.00 mm in diameter (tensileelastic modulus 40 GPa, tensile strength 1.7 GPa, elongation 6-8%) wastreated continuously by operating as shown in FIG. 1, but the surfaceroughening was omitted. Conditions in other sections were as follows: Inthe activating section 3, modifying agent: melted resorcinol at 120° C.,residence time: 0.5 seconds; in the adhesive applying section 5,adhesive: RFL liquid, residence time: 16 seconds; in the heat treatmentsection 6, temperature: 180° C., residence time: 1 minute. The thussurface-modified oriented polyacetal was wound up. Its elastic modulus,tensile strength, and adhesive strength to a rubber were found to 34GPa, 1.6 GPa, and 1150 g/mm², respectively.

EXAMPLES 51-55

An oriented polyacetal in filament form having properties shown in Table9 was sandblasted with alumina of No. 80 grade, and contacted with eachof the phenolic compounds (solvent-free) shown in Table 9 by dipping,and then air-dried or washed with water. Thereafter, RFL treatment andthen rubber adhesion were conducted in the same manner as in Examples1-7, thereby preparing composite specimens to evaluate the adhesivestrengths. Results of the evaluation are shown in Table 9.

                                      TABLE 9                                     __________________________________________________________________________           Oriented polyacetal                                                           Tensile elastic                                                                       Tensile                 Contact Contact                                                                            Withdrawal                                                                          Adhesive                   modulus strength                                                                           Elongation                                                                          Diameter                                                                           Modifying                                                                             temperature                                                                           time force strength                   (GPa)   (GPa)                                                                              (%)   (mm) agent   (°C.)                                                                          (min)                                                                              (kgf) (g/mm.sup.2)        __________________________________________________________________________    Example 51                                                                           40      1.7  6-8   1.00 Phenol  120     3    12.9  410                 Example 52                                                                           40      1.7  6-8   1.00 p-Chlorophenol                                                                        100     3    15.4  490                 Example 53                                                                           40      1.7  6-8   1.00 m-Cresol                                                                              120     3    12.9  410                 Example 54                                                                           40      1.7  6-8   1.00 Resorcinol                                                                            110     3    15.4  490                 Example 55                                                                           40      1.7  6-8   1.00 Pyrogallol                                                                            110     3    10.8  340                 Comparative                                                                          40      1.7  6-8   1.00 Acetone  50     3     4.0  130                 Example 6                                                                     __________________________________________________________________________

As can be seen from Table 9, phenolic compounds pertaining to thepresent invention, as compared with a compound used in ComparativeExample 6, can activate the surface of oriented polyacetal remarkably.

EXAMPLE 56

The same oriented polyacetal in filament form as used in Example 5 wassandblasted with alumina of No. 120 grade, immersed in a THF solution ofeach of several different phenolic compounds for 30 seconds at 23° C.,then taken out, and subjected to dry heat treatment at 160° C. for 10seconds. The treated polyacetals were placed separately in a mold, and a100° C. mixture of 90 parts of Adiprene L-100 (a prepolymer forpolyurethane supplied by Uniroyal Chemical Co.) and 10 parts of4,4'-methylene-bis(2-chloroaniline), a hardener, was poured into themold and hardened by heating at 100° C. for 60 minutes, formingcomposite specimens as shown in FIG. 2 to evaluate the adhesivestrengths. Results of the evaluation are shown in Table 10. Forcomparison, the above procedure was followed but using solvent THF alonefor the treatment. The adhesive strength found in this case is alsoshown in Table 10, from which it is demonstrated that the surfacemodification according to the present invention is also effective forsticking oriented polyacetals to polyurethane rubber.

                                      TABLE 10                                    __________________________________________________________________________           Oriented polyacetal                                                           Tensile elastic                                                               modulus  Tensile strength                                                                      Elongation                                                                          Diameter                                                                           Composition of                                                                            Withdrawal                                                                          Adhesive strength               (GPa)    (GPa)   (%)   (mm) modifying agent                                                                           force (kgf)                                                                         (g/mm.sup.2)             __________________________________________________________________________    Example 56                                                                           40       1.7     6-8   0.50 m-Aminophenol + THF                                                                        9.0  570                                                         (40 parts)   (60 parts)                    Example 57                                                                           40       1.7     6-8   0.50 Phloramine + THF                                                                          10.0  640                                                         (40 parts)   (60 parts)                    Example 58                                                                           40       1.7     6-8   0.50 3,5-dihydroxy- + THF                                                                      10.0  640                                                         benzyl alcohol                                                                (40 parts)   (60 parts)                    Example 59                                                                           40       1.7     6-8   0.50 3,5-dihydroxy- + THF                                                                      10.0  640                                                         benzyl chloride                                                               (40 parts)   (60 parts)                    Example 60                                                                           40       1.7     6-8   0.50 Resorcinol (40 parts)                                                                     10.0  640                                                         4,4'-methylene-bis(2-                                                         chloroaniline) (5 parts) +                                                    THF (55 parts)                             Comparative                                                                          40       1.7     6-8   0.50 THF alone    2.0  130                      Example 7                                                                     __________________________________________________________________________

EXAMPLES 61-71 AND COMPARATIVE EXAMPLE 8

An oriented polyacetal in filament form having properties shown in Table11 was rubbed uniformly with sandpaper of No. 80 grade, immersed in aTHF solution of 40 wt % of various different phenolic compounds for 30seconds, then taken out, and subjected to dry heat treatment at 160° C.for 10 seconds. An epoxy adhesive (trade name "Araldite"-supplied byCiba-Geigy Corp.) was applied on the treated polyacetals and cured bydry heat treatment at 100° C. for 10 minutes, forming compositespecimens as shown in FIG. 3. The polyacetal pieces in these specimenswere withdrawn to evaluate the adhesive strengths. Results of theevaluation are shown in Table 11. For comparison, the above procedurewas followed but using solvent THF alone for the treatment.

Table 11 demonstrates that the surface-modified oriented polyacetal andits production process of the present invention are also effective foradhesion to epoxy resin.

                                      TABLE 11                                    __________________________________________________________________________           Oriented polyacetal                                                           Tensile elastic                                                               modulus  Tensile strength                                                                      Elongation                                                                          Diameter                                                                           Phenolic compound                                                                         Withdrawal                                                                          Adhesive strength               (GPa)    (GPa)   (%)   (mm) (solvent)   force (kgf)                                                                         (g/mm.sup.2)             __________________________________________________________________________    Example 61                                                                           40       1.7     6-8   1.0  Catechor (THF)                                                                            33.0  1050                     Example 62                                                                           40       1.7     6-8   1.0  p-chlorophenol (THF)                                                                      32.0  1020                     Example 63                                                                           40       1.7     6-8   1.0  Resorcinol (THF)                                                                          29.0  920                      Example 64                                                                           40       1.7     6-8   1.0  3,5-Xylenol (THF)                                                                         26.6  850                      Example 65                                                                           40       1.7     6-8   1.0  o-Nitrophenol (THF)                                                                       25.4  810                      Example 66                                                                           40       1.7     6-8   1.0  Phenol (THF)                                                                              24.4  780                      Example 67                                                                           40       1.7     6-8   1.0  3,5-dihydroxy-benzoic                                                                     24.0  760                                                         acid (THF)                                 Example 68                                                                           40       1.7     6-8   1.0  Pyrogallol (THF)                                                                          21.0  670                      Example 69                                                                           40       1.7     6-8   1.0  Gallic acid (THF)                                                                         20.0  640                      Example 70                                                                           40       1.7     6-8   1.0  m-Aminophenol (THF)                                                                       19.5  620                      Example 71                                                                           40       1.7     6-8   1.0  2,4-Dihydroxy-                                                                            19.0  610                                                         benzaldehyde (THF)                         Comparative                                                                          40       1.7     6-8   1.0  None (THF)  18.0  590                      Example 8                                                                     __________________________________________________________________________

EXAMPLE 72 AND COMPARATIVE EXAMPLE 9

An oriented polyacetal in filament form of 2.0 mm in diameter (tensileelastic modulus 35 GPa, tensile strength 1.6 GPa, elongation 5-6%) wasrubbed uniformly with sandpaper of No. 80 grade, dipped in a methanolicsolution containing 40 wt % of resorcinol for 30 seconds, and thenair-dried. A composite specimen as shown in FIG. 3 was prepared bywelding or melt-adhering Duracon M 25-04 (the registered trademark of anacetal copolymer supplied by Polyplastic Co., Ltd.) at 175° C. around anend portion of a piece of the treated polyacetal by using an injectionmolding system. The polyacetal piece was withdrawn from the acetalcopolymer resin to evaluate the adhesive strength. The found withdrawalforce and adhesive strength were 94.2 Kg and 1500 g/mm², respectively.When no treatment was carried out except rubbing with the samesandpaper, the withdrawal force and adhesive strength were 62.8 Kg and1000 g/mm², respectively (Comparative Example 9).

EXAMPLE 73

An oriented polyacetal in tape form 0.2 mm thick 5.0 mm wide (tensileelastic modulus 40 GPa, tensile strength 1.7 GPa, elongation 6-8%) wasapplied uniformly on the polyacetal tape rubbed with a sand paperpreviously. Portions 10 mm long of two pieces of the resorcinol-coatedtape were stuck together and compressed by a press at 160° C. and 10Kg/cm² for 10 seconds. The resulting specimen was subjected to a tensileshear test and the stress at rupture and the adhesive strength wereevaluated. The found stress and adhesive strength were 75 Kg and 1500g/mm², respectively.

EXAMPLE 74

An oriented polyacetal fiber of 1.3 mm in diameter (tensile elasticmodulus 40 GPa, tensile strength 1.7 GPa, elongation 5-7%) was treatedcontinuously by operating as shown in FIG. 1. The surface roughening wasperformed by sandblasting with alumina of No. 120 grade. In theactivating section 3, a resorcinol (40 parts)-RF liquid (60 parts)mixture (RF liquid is Preparation Example 2) was applied as a modifyingagent in a residence time of 16 seconds; in the heat treatment section4, the fiber was heated at 160° C. during a residence time of 30seconds; in the adhesive applying section 5, an RFL liquid (PreparationExample 3) was applied in a residence time of 16 seconds; then in theheat treatment section 6, the fiber was heated at 175° C. underrelaxation during a residence time of 2.5 minutes; and the treated fiberwas wound up. This fiber was coated with a crude rubber for automotivetire carcasses to prepare a 5-wind bead of 588 mm in diameter. A bicycletire was formed by using this bead. The tensile stress of the beadportion of this tire was found to be 1015 kg (retention 90%). The beadand the rubber were completely adhered together.

EXAMPLE 75

An oriented polyacetal fiber of 1.3 mm in diameter (tensile elasticmodulus 40 GPa, tensile strength 1.7 GPa, elongation 5-7%) was treatedcontinuously by operating as shown in FIG. 1. The surface roughening wasperformed by sandblasting with alumina of No. 120 grade. In theactivating section 3, an aqueous solution of 40 wt % of resorcinol wasapplied as a modifying agent in a residence time of 16 seconds; in theheat treatment section 4, the fiber was heated at 160° C. during aresidence time of 16 seconds; in the adhesive applying section 5, anepoxy adhesive (Registered Trade Mark "Araldite" supplied by Ciba-GeigyCorp.) was applied; then in the heat treatment section 6, the fiber washeated at 175° C. under relaxation during a residence time of 2.5minutes; and the treated fiber was wound up. An epoxy resin was adheredto this fiber to form a 5-wind bead of 588 mm in diameter. A bicycletire was formed by using this bead. The tensile stress of the beadportion of this tire was found to be 1015 Kg (retention 90%).

EXAMPLE 76

A twine consisting of 7 oriented polyacetal fibers of 1.0 mm in eachdiameter (tensile elastic modulus 40 GPa, tensile strength 1.7 GPa,elongation 6-8%) was prepared and sandblasted with alumina of No. 120grade. An aqueous solution containing 40 wt % of resorcinol was appliedon the twine, and dried at 120° C. to coat resorcinol uniformly on thetwine. This treated twine was further coated with a polyacetal copolymer(Duracon M 25-04, supplied by Polyplastic Co., Ltd.) by using anextruder, forming a rope. The tensile stress of this rope was found tobe 1015 kg (retention 90%) and the core material and the coatingmaterial of this rope were completely adhered together. The flexibilityand the flexural-fatigue resistance of this rope were improved by afactor of about two over those of the uncoated twine.

EXAMPLE 77

An oriented polyacetal fiber of 0.5 mm in diameter (tensile elasticmodulus 40 GPa, tensile strength 1.7 GPa, elongation 6-8%) wassandblasted with alumina of No. 120 grade, immersed in an aqueoussolution containing 40 wt % of resorcinol, then taken out, and subjectedto dry heat treatment at 160° C. for 20 seconds. The treated fiber waswound 50-wind densely in parallel around a flat frame, and an epoxyresin was adhered on these fibers and cured by hot pressing at 5 kg/cm²and 140° C. for 5 minutes to form a composite sheet 100 mm long, 28 mmwide, and 0.7 mm thick. The longitudinal tensile elastic modulus and theflexural elastic modulus of this sheet were 730 kg/mm² and 570 kg/mm²,respectively.

EXAMPLE 78

An oriented polyacetal fiber of 0.5 mm in diameter (tensile elasticmodulus 40 GPa, tensile strength 1.7 GPa, elongation 6-8%) wassandblasted with alumina of No. 120 grade, immersed in a modifying agentconsisting of 40 parts of resorcinol, 5 parts of 6% cobalt naphthenate,and 55 parts of methanol, then taken out, and subjected to dry heattreatment at 160° C. for 20 seconds. 40 Pieces of fibers cut off fromthe treated fiber were placed side-by-side in a mold, and a liquidmixture composed of 98 parts of an unsaturated polyester (supplied byTakeda Chemical Industries, Ltd. under the registered trademark ofpolymal 3308), 0.8 part of 6% cobalt naphthenate, 1.1 parts of methylethyl ketone peroxide, and 0.1 part of N,N-dimethylaniline was pouredinto the mold, cured at 23° C., and then heated at 60° C. for 60minutes, thereby forming a plate 150 mm long, 10 mm wide, and 4 mmthick. The longitudinal tensile elastic modulus and the flexural elasticmodulus of this plate were 820 kg/mm² and 570 kg/mm². In contrast, asimilar plate but containing no oriented polyacetal tube showed atensile elastic modulus of 380 kg/mm² and a flexural elastic modulus of380 kg/mm².

EXAMPLE 79

An oriented polyacetal fiber of 0.2 mm in diameter (tensile elasticmodulus 40 GPa, tensile strength 1.7 GPa, elongation 6-8%) wassandblasted with alumina of No. 240 grade, immersed in an aqueoussolution containing 40 wt % of resorcinol for 10 seconds, then takenout, subjected to dry heat treatment at 160° C. for 10 seconds, and cutinto pieces 24 mm long. A uniform mixture of 82 parts of these shortfilaments, 326 parts of Portland cement, 851 parts of sand, 826 parts ofcoarse aggregate (sand of up to 25 mm in diameter), and 212 parts ofwater was poured in a mold and left standing to cure, thereby forming aconcrete plate. The flexural strength of this plate 28 days later wasfound to be 350 kg/cm². On the other hand, the flexural strength of acontrol plate containing no oriented polyacetal, 28 days later, was 250kg/cm².

EXAMPLE 80

An oriented polyacetal in tape form 0.2 mm thick and 2 mm wide (tensileelastic modulus 40 GPa, tensile strength 1.7 GPa, elongation 6-8%) wassandblasted with alumina of No. 240 grade. This tape was knitted to forma net consisting of 20-mm square lattices. This net was immersed in amethanolic solution of 40 wt % of m-aminophenol for 10 seconds, thentaken out, and subjected to dry heat treatment at 160° C. for 10seconds. An epoxy adhesive (trade name Polymortar E21, supplied by KowaKasei Co., Ltd.) for concrete member purposes was applied on the treatednet and cured. Three coated nets prepared in this way were superposed atintervals of 2 mm and placed in a mold, and a slurry composed of 600parts of cement, 1200 parts of sand, and 360 parts of water was pouredinto the mold and left standing to harden, thereby forming a concreteplate 10 mm thick. The flexural strength of this plate 28 days later wasfound to be 430 kg/cm² On the other hand, the flexural strength of acontrol plate containing no oriented polyacetal net, 28 days later, was230 kg/cm².

We claim:
 1. An oriented polyacetal product having a tensile elasticmoduli of at least 4 GPa and tensile strength of at least 0.6 GPa, thesurface of said product being coated partly or entirely with a phenoliccompound composite layer comprising polyacetal and a reaction product ofsaid polyacetal and a phenolic compound.
 2. A modified orientedpolyacetal product according to claim 1, wherein said layer furthercomprises a resorcinol-formaldehyde condensate or aresorcinol-formaldehyde-latex.
 3. An elastomer or plastic product whichis reinforced by the modified oriented polyacetal product as claimed inclaims 1 or
 2. 4. A tire bead comprising the modified orientedpolyacetal product as claimed in claims 1 or
 2. 5. A rope, cable or cordcomprising a modified oriented polyacetal product as claimed in claims 1or
 2. 6. A surface-modified oriented polyacetal product, having atensile elastic moduli of at least 4 GPa and a tensile strength of atleast 0.6 GPa, being produced by a process comprising the step ofapplying a phenolic compound to part or all of the surface of saidoriented polyacetal product, to thereby phenolate said orientedpolyacetal product and to form a composite layer having a phenolicgradient that is richer nearer to the surface of said orientedpolyacetal product.